Free online MIDI converter

midee converts MIDI files to MP3, WAV, and MP4 in the browser. Drop in a .mid file, listen to it with a sampled instrument, and export whichever format you need from one dialog. Nothing is uploaded, there is no account, and the output carries no watermark.

This page is the overview. Each format has its own guide with the exact settings, file sizes, and limitations.

Which format do you need?

If you are unsure, start with MP3. It is the smallest and plays everywhere. Switch to WAV only when the file is going into another piece of software for further work.

How the conversion works

Every conversion starts the same way. The MIDI is parsed into notes, tempo changes, and sustain-pedal events, then performed by one of 13 multi-sampled instruments inside a Web Audio OfflineAudioContext. That render is faster than real time and does not depend on your sound card.

From there the paths split:

• MP3 encodes the render with the LAME encoder running in JavaScript, at 192 kbps constant bitrate.
• WAV writes the render as uncompressed 16-bit PCM.
• MP4 encodes the render to AAC, draws a piano-roll video frame by frame with the browser's hardware H.264 encoder, and muxes both into an MP4.

All three run in your tab. Once the app and the instrument's samples have loaded, the export completes without a network connection.

Choosing the instrument

A MIDI file has no sound of its own, so the instrument decides what the converted file sounds like. midee's instruments are multi-sampled recordings, not a General MIDI synth: Piano, Upright, Digital, Rhodes, Guitar, Violin, Flute, Marimba, Bells, Strings, Pad, Pluck, and Bass. Audition them with the play button before you export.

One instrument is used for the whole file. If your MIDI contains several parts written for different instruments, mute the tracks that do not suit the instrument you pick, or export each part separately.

Browser support

MP3 and WAV need only the standard Web Audio API. MP4 additionally needs WebCodecs for video encoding, which is why it has version requirements.

What midee does not convert

• Audio to MIDI. MP3 to MIDI or WAV to MIDI is transcription, a separate problem that midee does not attempt.
• MIDI to sheet music, PDF, or MusicXML. midee shows a piano roll, not notation.
• Batch jobs. Files are converted one at a time.
• Other audio formats. OGG, FLAC, and AAC-only files are not offered. Export WAV and convert with another tool if you need them.

Frequently asked questions

Is the MIDI converter free? Yes. midee is open source. There is no paid tier, no signup, and no watermark on any output.

Does midee upload my MIDI file? No. Parsing, rendering, encoding, and saving all run inside the browser tab.

What is the difference between MP3 and WAV output? Both are made from the same render. WAV stores it losslessly and is about 10 MB per minute. MP3 compresses it to about 1.4 MB per minute at 192 kbps, which is fine for listening but not ideal as a source for further editing.

Can I convert a MIDI file on my phone? Yes. MP3 and WAV export work in mobile browsers. MP4 export also works where the mobile browser supports WebCodecs, which includes current Chrome on Android and Safari on iOS 16.4 and later.

Does it read the instruments in my MIDI file? No. midee plays every track with the one instrument you select and ignores General MIDI program changes.

Try it

Open midee, drop in a .mid file, choose an instrument, and pick a format in the export dialog. Read the MIDI to MP3, MIDI to WAV, or MIDI to MP4 guide for the details of each output. If you just want to play the file, the online MIDI player is the same app without the export step.